Rule – Use a comma to separate the city from the state, and always put one after the state, also.Example:I lived in Denver, Colorado, for 20 years.

NOTE: The U.S. Postal Service’s two-letter capitalized abbreviations (e.g., CO for Colorado, IL for Illinois) are not recommended in formal writing. However, when writing an address on an envelope, you should follow U.S. Postal Service guidelines. These guidelines are covered in our blog “Writing Addresses.”

Rule – Use commas to set off expressions that interrupt sentence flow.Example:I am, as you have probably noticed, very nervous about this.

Pop Quiz

1A. The New England Patriots, have played their home football games in Foxborough, Massachusetts, since 1971.
1B. The New England Patriots have played their home football games in Foxborough, Massachusetts since 1971.
1C. The New England Patriots have played their home football games in Foxborough, Massachusetts, since 1971.

2A. Janet has lived in New Orleans, Louisiana, her entire life.
2B. Janet has lived in New Orleans, Louisiana her entire life.
2C. Janet, has lived in New Orleans, Louisiana, her entire life.

3A. I agreed, although I regretted the decision later, to loan our car to Miriam.
3B. I agreed although I regretted the decision later, to loan our car to Miriam.
3C. I agreed although I regretted the decision later to loan our car to Miriam.

Pop Quiz Answers

1C. The New England Patriots have played their home football games in Foxborough, Massachusetts, since 1971.

2A. Janet has lived in New Orleans, Louisiana, her entire life.

3A. I agreed, although I regretted the decision later, to loan our car to Miriam.

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